1. Field of the Invention
This invention relates generally to a plane type multi-digit fluorescent indicating apparatus for use in, for example, small electronic calculators and to a method of manufacture thereof.
2. Description of the Prior Art
There are various conventional structures for multi-digit fluorescent indicator tubes and multi-digit fluorescent indicating apparatuses (hereinafter called indicating apparatuses). The pattern indicating portion of these tubes, comprises a group of segmented electrodes, on which the fluorescent material is deposited, disposed on a base plate composed of insulating material, such as ceramic for example. The indicator electrode assembly is formed by disposing a grid and a cathode opposing the pattern indicating portion. Then, the indicator electrode assembly is put inside an enclosure such as a cylindrical glass tube, or an enclosure formed by hermetically sealing together two base plates, one of which includes a transparent window portion and which may be shaped like an inverted flat-bottom boat. A stem portion having hermetically sealed lead-in wires passing through may also be provided on at least one end thereof. In such a conventional structure, the indicator electrode assembly normally has a plural number pattern indicating portion, and the stem portion is formed separately after combining and connecting the components together. Therefore, these conventional devices are extremely complicated due to many internal connecting wires being required in a congested enclosure. Furthermore, in conventional devices minimization of dimensions is difficult and the labour necessary for assembly and making internal connections is extensive. Furthermore, there is a difficulty in that adequate reliability could not be maintained due to the large number of internal connections made by welding.
In order to overcome the aforementioned problems in the conventional apparatus, the indicating apparatus disclosed in U.S. application Ser. No. 307,368 filed Nov. 17, 1972, now abandoned has been proposed. This apparatus is illustrated in FIGS. 1 and 2.
In FIGS. 1 and 2, a print base plate 1a is formed by depositing on a base plate 1, composed of insulating material such as glass or ceramic, conductive films forming electric connecting wirings 3, lead-in wires 4 and terminals 5. The conductive film is covered with an insulating film 6 which is provided with a plurality of holes for permitting the connecting wires 3 to communicate with each of segmented electrodes 2a-2h. An anode pattern indicating portion is formed by depositing a fluorescent material 7 on the segmented electrode 2a-2h. Plural grids 8 and cathodes 9, emitting thermal electrons, are positioned opposite each group of the segmented electrodes 2a-2h, and are connected to the connecting wire 3 by a conductive adhesive agent 10 and secured to print base plate 1a. These portions of the electrodes on the base plate are installed inside an evacuated air tight enclosure comprising the print base plate 1a and an upper surface window plate 11 sealed to the upper surface of the base plate. In addition, the terminals 5 are printed on the base plate 1a for connection to outside circuits and are positioned outside the enclosure. In other words, the conductive films of connecting wires formed on base plate 1 are extended to the outside of the enclosure as the terminals for each electrode.
In the indicating apparatus described above, the construction and assembly of the parts may be simplified. Thereby minimization of the size of the indicating apparatus can be accomplished with considerable ease. Moreover, since a conductive adhesive agent is employed on many connecting portions inside, there is an advantage in that the working properties and the reliability of the device can be considerably improved. However, in manufacturing an indicating apparatus with such a construction, the grid 8 and cathode 9 are required to be installed respectively on the base plate in correct relationship with respect to each of the segmented electrodes 2a-2h. This brings about a problem in that, in assembling these electrodes, complicated and accurate tools are required and a considerable amount of labour is necessitated. Futhermore, in the described indicating apparatus printed terminals formed of conductive films deposited on the base plate are used as terminals for connecting outside circuits to the apparatus. Thus, complicated socket structures having resilient internal contacts are required for mating with these printed terminals. Such terminal connectors are expensive because of their construction which requires considerable precision.